VMware has become synonymous with virtualization, but Microsoft is in the game, too. Today, however, the software giant told its customers it will have to wait for its latest.

In a blog post, Mike Neil, general manager of Microsoft's virtualization strategy, said that Virtual Server 2005 R2 service pack 1, which has been in beta testing since mid-2006 and was originally due in the first quarter, will instead see the light during the second-quarter. But there is a release candidate available for testing.

As for the first public beta of Windows Server virtualization, codenamed Viridian, Neil said it will now be available in the second half of 2007, not in the first half as Microsoft previously said.

The company still plans to ship Viridian within 180 days of the launch of Longhorn Server, the next release of its server software, which is still on track for release in the second half of the year. Beta 3 of Windows Server Longhorn is scheduled for the first half of the year.

Neil said the change in plans for Viridian stemmed from concerns over drivers, performance and scalability. "In an IT environment of ever-growing multi-core processor systems, Windows Server virtualization is being designed to scale across a much broader range of systems than the competition," Neil wrote.

Microsoft is designing it to scale up to 64 processors, which Neil claimed is something no other vendors' product supports, as well as offering features such as hot-addition of processors, memory, disk and networking, as well as a greater scalability with more SMP support and memory.

Peter Pawlak, senior analyst for Directions on Microsoft, said it hurts Microsoft every day Viridian and the Virtual Server service pack are late. "Every day they delay that thing is a day they lose customers to VMware, and they can only keep the FUD thing going for so long before people get fed up and just buy VMware," he told internetnews.com.

VMware has done a little counter-FUD of its own, saying Microsoft is trying to impinge customers' freedom to "choose virtualization software by limiting who can run their software and how they can run it."

The issue Pawlak doesn't understand is why it's taking so long. "Are they woefully underestimating the magnitude of the project? I'm not sure," he said. "VMware has been out long enough that they knew what they had to do to beat [Microsoft] for this to be a success," he said.